This invention relates generally to surveillance systems and, in particular, to a method and apparatus for controlling a video surveillance display.
Displaying the video data gathered by video surveillance systems has been a challenge because of the large amount of data involved. If the video data is compressed, such as with MPEG video, the system must first decompress or decode the video before it can be displayed. This decompression can require a significant amount of system resources and time. In order to display multiple compressed video streams, the system must be capable of handling the multiple decompressions. Depending upon the number of video streams to be displayed simultaneously, the resolution of each stream, and the frame rate requested by the system user for each displayed video stream, the system resources can quickly be exceeded. Full-motion video provides the most information and is preferred by many users. However, the amount of system resources required to display a plurality of video streams in full-motion video can be significant thereby further taxing the system resources. With intraframe encoded images, such as JPEG images, each one is independent so that if the system is displaying a series of JPEG images and finds that it cannot handle the frame per second rate, then the system can simply display every other image or every third or fourth image depending on the current limitation of the system resources. With MPEG video, the system has to be able to decode the whole stream. If the system falls behind, you cannot eliminate some of the data by simply displaying every other image as is done with an intraframe encoded stream. As a result, the system ends up with more video data coming in than is being processed which can result in the system crashing. In addition, temporary overloads of the system can result, for example, from a burst of data caused by network traffic or interruption of system processing power caused by internal system processes or a user's request. These temporary overloads can be extremely troublesome if the system resources are stretched to the maximum. A system crash or significant reduction in the level of service is unacceptable in the video surveillance environment where continuous operation and the maximum possible amount of information is required.
Accordingly, there has been a long felt need in the video surveillance industry for a video surveillance system that maximizes the amount of video information displayed while minimizing interruptions of the displayed video.